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A373575
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Numbers k such that k and k-1 both have at least two distinct prime factors. First element of the n-th maximal antirun of non-prime-powers.
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14
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1, 15, 21, 22, 34, 35, 36, 39, 40, 45, 46, 51, 52, 55, 56, 57, 58, 63, 66, 69, 70, 75, 76, 77, 78, 85, 86, 87, 88, 91, 92, 93, 94, 95, 96, 99, 100, 105, 106, 111, 112, 115, 116, 117, 118, 119, 120, 123, 124, 130, 133, 134, 135, 136, 141, 142, 143, 144, 145
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OFFSET
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1,2
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COMMENTS
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The last element of the same antirun is given by A255346.
An antirun of a sequence (in this case A361102) is an interval of positions at which consecutive terms differ by more than one.
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LINKS
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EXAMPLE
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The maximal antiruns of non-prime-powers begin:
1 6 10 12 14
15 18 20
21
22 24 26 28 30 33
34
35
36 38
39
40 42 44
45
46 48 50
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MATHEMATICA
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Select[Range[100], !PrimePowerQ[#]&&!PrimePowerQ[#-1]&]
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CROSSREFS
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Runs of prime-powers:
Runs of non-prime-powers:
Antiruns of prime-powers:
Antiruns of non-prime-powers:
A057820 gives first differences of consecutive prime-powers, gaps A093555.
A356068 counts non-prime-powers up to n.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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